JP5802632B2 - Method for manufacturing silicon carbide semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a silicon carbide semiconductor device.

  As a semiconductor material, a compound semiconductor such as silicon carbide four-layer periodic hexagonal crystal (4H-SiC) is known. In manufacturing a power semiconductor device using 4H—SiC as a semiconductor material, a 4H—SiC single crystal film (hereinafter referred to as a SiC epitaxial film) is formed on a semiconductor substrate (hereinafter referred to as 4H—SiC substrate) made of 4H—SiC. ) Is epitaxially grown to produce a SiC single crystal substrate. Conventionally, a chemical vapor deposition (CVD) method is known as an epitaxial growth method (see, for example, Patent Document 1 below).

Specifically, the epitaxial growth by the chemical vapor deposition method is performed by thermally decomposing a source gas flowing in a reaction vessel (chamber) in a carrier gas, and following a crystal lattice of a 4H-SiC substrate to form silicon (Si) atoms. By continuously depositing, a SiC epitaxial film is grown on the 4H-SiC substrate. In general, monosilane (SiH ₄ ) gas and dimethylmethane (C ₃ H ₈ ) gas are used as the source gas, and hydrogen (H ₂ ) gas is used as the carrier gas. Further, nitrogen (N ₂ ) gas or trimethylaluminum (TMA) gas is appropriately added as a doping gas.

Special table 2009-508799 gazette

  However, in the conventional epitaxial growth method, the growth rate is as low as about several μm / h, and the epitaxial film cannot be grown very fast. For example, in order to manufacture a SiC semiconductor device that achieves a high breakdown voltage of 10 kV or more, it is necessary to grow a 4H—SiC single crystal film with a thickness of at least about 100 μm on a 4H—SiC substrate. For this reason, there is a big industrial problem, for example, the yield in the production line of semiconductor devices is low.

  In addition, the inventors' diligent research newly found that sulfur (S) and chlorine (Cl) may be incorporated as impurities into the SiC epitaxial film grown by the conventional epitaxial growth method. The impurities taken into the SiC epitaxial film become defects and cause deterioration of the crystal quality of the SiC epitaxial film or shorten the carrier lifetime. For this reason, there is a problem that it is difficult to grow an optimal SiC epitaxial film for manufacturing a semiconductor device.

  An object of the present invention is to provide a method for manufacturing a silicon carbide semiconductor device capable of growing a silicon carbide semiconductor film at a high speed in order to solve the above-described problems caused by the prior art. Another object of the present invention is to provide a method for manufacturing a silicon carbide semiconductor device capable of growing a silicon carbide semiconductor film having a high crystal quality in order to eliminate the above-described problems caused by the prior art.

  In order to solve the above-described problems and achieve the object of the present invention, a method for manufacturing a silicon carbide semiconductor device according to the present invention uses a gas containing silicon and a gas containing carbon as a source gas, and chlorine is added to the source gas. A step of growing a silicon carbide semiconductor film on a silicon carbide semiconductor substrate using a hydrogen gas as a carrier gas by adding a gas containing fluorine and a gas containing fluorine, with respect to the number of silicon atoms in the silicon-containing gas The chlorine-containing gas is added within a range where the ratio of the number of chlorine atoms is 2.0 to 5.0, and the ratio of the number of fluorine atoms to the number of hydrogen atoms in the carrier gas is 0 The gas containing fluorine is added within a range of 1 or more and less than 0.2.

  In addition, the method for manufacturing a silicon carbide semiconductor device according to the present invention is characterized in that, in the above-described invention, the content of sulfur remaining in the silicon carbide semiconductor film is 0.02 ppm or less.

  In addition, the method for manufacturing a silicon carbide semiconductor device according to the present invention is characterized in that, in the above-described invention, the content of chlorine remaining in the silicon carbide semiconductor film is 0.1 ppm or less.

  In the method for manufacturing a silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the gas containing chlorine is hydrogen chloride gas or chlorine gas.

  Moreover, the method for manufacturing a silicon carbide semiconductor device according to the present invention is characterized in that, in the above-described invention, the gas containing fluorine is a carbon tetrafluoride gas.

  A method for manufacturing a silicon carbide semiconductor device according to the present invention is characterized in that, in the above-described invention, the silicon carbide semiconductor film made of a single crystal is grown by chemical vapor deposition.

  According to the above-described invention, the amount of the source gas introduced that contributes to the growth of the silicon carbide semiconductor film can be increased by adding the gas containing chlorine to the source gas. As a result, the growth rate of the silicon carbide semiconductor film can be increased by about 20 times compared to the conventional method for manufacturing a silicon carbide semiconductor device to which no gas containing chlorine is added.

  Further, according to the above-described invention, by adding a gas containing chlorine and a gas containing fluorine to the raw material gas, chlorine and fluorine react with sulfur which is an impurity in the silicon carbide semiconductor film, and the chloride system Further, it can be discharged to the outside of the silicon carbide semiconductor film as a fluoride-based gas. For this reason, impurities (sulfur and chlorine) remaining in the silicon carbide semiconductor film and impurities contained in the silicon carbide semiconductor substrate can be prevented from being taken into the silicon carbide semiconductor film. Thereby, impurities remaining in the silicon carbide semiconductor film can be reduced. Therefore, it is possible to grow a silicon carbide semiconductor film with much fewer impurities than conventional.

  Further, according to the above-described invention, by introducing a gas containing silicon, a gas containing carbon, a gas containing chlorine, and a gas containing fluorine at an appropriate mixing ratio, silicon, during the growth of the silicon carbide semiconductor film, Impurities other than n-type and p-type elements for doping carbon and the silicon carbide semiconductor film can be made difficult to remain in the silicon carbide semiconductor film. Therefore, the silicon carbide semiconductor film can be grown at a high speed, and impurities that cause deterioration of the characteristics of the silicon carbide semiconductor film remaining in the silicon carbide semiconductor film can be reduced.

  According to the method for manufacturing a silicon carbide semiconductor device of the present invention, there is an effect that the silicon carbide semiconductor film can be grown at a high speed. Moreover, according to the manufacturing method of the silicon carbide semiconductor device concerning this invention, there exists an effect that a silicon carbide semiconductor film with high crystal quality can be grown.

3 is a flowchart showing an outline of a method for manufacturing the silicon carbide semiconductor device according to the first embodiment; It is sectional drawing which shows the state in the middle of manufacture of the silicon carbide semiconductor device concerning Embodiment 1. FIG. FIG. 6 is a characteristic diagram showing a relationship between a raw material gas introduction amount and an epitaxial film growth rate in the method for manufacturing a silicon carbide semiconductor device according to the first embodiment; 3 is a chart showing components of an epitaxial film grown by the method for manufacturing a silicon carbide semiconductor device according to Example 1. FIG. 7 is a chart showing components of an epitaxial film grown by a method for manufacturing a silicon carbide semiconductor device according to Example 2. FIG. FIG. 6 is a characteristic diagram showing a relationship between a gas introduction amount and an epitaxial film growth rate in the method for manufacturing a silicon carbide semiconductor device according to the second embodiment.

  Exemplary embodiments of a method for manufacturing a silicon carbide semiconductor device according to the present invention will be described below in detail with reference to the accompanying drawings. Note that, in the following description of the embodiments and the accompanying drawings, the same reference numerals are given to the same components, and duplicate descriptions are omitted.

(Embodiment 1)
The method for manufacturing a silicon carbide semiconductor device according to the first embodiment will be described by taking as an example the case of manufacturing (manufacturing) a semiconductor device using a silicon carbide four-layer periodic hexagonal crystal (4H—SiC) as a semiconductor material. FIG. 1-1 is a flowchart illustrating an outline of a method for manufacturing the silicon carbide semiconductor device according to the first embodiment. FIG. 1-2 is a cross sectional view showing a state in the process of manufacturing the silicon carbide semiconductor device according to the first embodiment. First, a substrate (4H—SiC substrate) 1 made of 4H—SiC is prepared and cleaned by a general organic cleaning method or RCA cleaning method (step S1).

Next, in a reaction furnace (chamber, not shown) for growing a 4H-SiC single crystal film (hereinafter referred to as a SiC epitaxial film (silicon carbide semiconductor film)) 2 by a chemical vapor deposition (CVD) method, The 4H—SiC substrate 1 is inserted (step S2). Next, the inside of the reaction furnace is evacuated to a vacuum degree of 1 × 10 ⁻³ Pa or less, for example. Next, hydrogen (H ₂ ) gas purified by a general purifier is introduced into the reaction furnace at a flow rate of 20 L / min for 10 minutes, and the reaction furnace is placed in an H ₂ atmosphere (step S3).

Next, the surface of the 4H—SiC substrate 1 is cleaned by chemical etching with H ₂ gas (step S4). Specifically, the reactor is heated, for example, by high frequency induction while introducing H ₂ gas at 20 L / min. And the inside of a reaction furnace is raised to 1600 degreeC, The surface of 4H-SiC board | substrate 1 is cleaned by hold | maintaining for 10 minutes at this temperature. The temperature in the reaction furnace is measured, for example, with a radiation thermometer.

Next, with the H ₂ gas introduced in step S3 introduced as a carrier gas at a flow rate of 20 L / min, a source gas, a gas added to the source gas (hereinafter referred to as an additive gas), and a doping gas are introduced into the reactor. (Step S5). In FIG. 1-2, the source gas, additive gas, doping gas, and carrier gas are collectively indicated by arrow 3. A description of the source gas, additive gas, doping gas, and carrier gas will be given later.

  Next, the SiC epitaxial film 2 is grown on the surface of the 4H—SiC substrate 1 by chemical vapor deposition (CVD) using the source gas, additive gas, doping gas and carrier gas introduced in step S5. Specifically, the 4H-SiC substrate 1 is heated in a reaction furnace, and the SiC epitaxial film 2 is grown by thermally decomposing the source gas with a carrier gas. Thereby, the SiC single crystal substrate 10 in which the SiC epitaxial film 2 is laminated on the 4H—SiC substrate 1 is manufactured (step S6). Thereafter, a desired element structure (not shown) is formed on SiC single crystal substrate 10 (step S7), and the SiC semiconductor device is completed.

Next, the source gas, additive gas, doping gas, and carrier gas introduced into the reaction furnace in step S5 will be described. As the source gas, a gas containing silicon (Si) and a gas containing carbon (C) are used. The gas containing Si may be, for example, a monosilane (SiH ₄ ) gas diluted with H ₂ . The gas containing C may be, for example, dimethylmethane (C ₃ H ₈ ) gas diluted with H ₂ .

A gas containing chlorine (Cl) is used as the additive gas. That is, in step S6, epitaxial growth is performed by a halide CVD method using a halogen compound. The gas containing Cl may be, for example, high-purity (for example, 100% purity) hydrogen chloride (HCl) gas or Cl ₂ gas filled in a high-pressure gas container (cylinder). Further, the gas containing Cl is preferably introduced in a range where the ratio of the number of Cl atoms to the number of Si atoms in the gas containing Si is 2.0 or more and 5.0 or less. The reason will be described later. By adding a gas containing Cl to the source gas, a large amount of source gas can be introduced, and high-speed epitaxial growth can be realized.

Further, a gas containing fluorine (F) is used as the additive gas. The gas containing F is preferably, for example, carbon tetrafluoride (CF ₄ ) gas. This is because, in addition to elements contained in the CF ₄ gas is F the effects of the present invention, since only C, which is a main component of the SiC epitaxial film 2, the SiC epitaxial influence of the addition of CF ₄ gas This is because it does not occur in the film 2. Further, the gas containing F is preferably added in a range where the ratio of the number of F atoms to the number of H atoms in the carrier gas (F / H ratio) is 0.1 or more and less than 0.2. . The reason will be described later. As the doping gas, for example, nitrogen (N ₂ ) gas or trimethylaluminum (TMA) gas may be used. Doping gas may or may not be added.

  Further, by using a gas containing Cl as the additive gas and a gas containing source gas and F, Cl and F in the additive gas react with impurities such as Cl and sulfur (S) in the SiC epitaxial film 2. Then, it can be discharged to the outside of the SiC epitaxial film 2 as a chloride or fluoride gas. Thereby, impurities remaining in SiC epitaxial film 2 can be reduced. The impurities in the SiC epitaxial film 2 are components other than Si and C in the source gas and components in the doping gas, and are components that cause the characteristics of the SiC epitaxial film 2 to deteriorate.

  The Cl content remaining in the SiC epitaxial film 2 is preferably 0.1 ppm or less. The reason is as follows. By using a gas containing Cl as the additive gas, the SiC epitaxial film 2 is grown at a high speed as described above, and there is a high possibility that a large amount of Cl in the gas containing Cl is taken into the SiC epitaxial film 2 as an impurity. . By setting the content of Cl remaining in SiC epitaxial film 2 to 0.1 ppm or less, a desired growth rate of SiC epitaxial film 2 can be obtained, and characteristic deterioration of SiC epitaxial film 2 can be prevented. Because it can.

  The S content remaining in the SiC epitaxial film 2 is preferably 0.02 ppm or less. The reason is as follows. S in the SiC epitaxial film 2 causes the characteristics of the SiC epitaxial film 2 to deteriorate as described above. For this reason, it is desirable not to leave S which is an impurity in the SiC epitaxial film 2. The content of S remaining in the SiC epitaxial film 2 is, for example, 0.02 ppm or less which is a measurement limit value of a glow discharge mass spectrometry (GDMS) apparatus, for example, so that the characteristics of the SiC epitaxial film 2 are deteriorated. Can be prevented.

In order to make the content of S remaining in the SiC epitaxial film 2 0.02 ppm or less, the gas containing F is a ratio of the number of F atoms to the number of H atoms in the H ₂ gas as a carrier gas (F / H It is desirable to add such that the ratio is 0.1 or more. This is because when the F / H ratio is less than 0.1, S that is an impurity in the SiC epitaxial film 2 cannot be sufficiently removed. Moreover, it is desirable to add the gas containing F so that the F / H ratio is less than 0.2. The reason is that when the F / H ratio is 0.2 or more, F newly increases as an impurity in the SiC epitaxial film 2.

  Next, the relationship between the amount of source gas introduced and the growth rate of SiC epitaxial film 2 will be described. FIG. 2 is a characteristic diagram showing the relationship between the amount of introduced raw material gas and the growth rate of the epitaxial film in the method for manufacturing the silicon carbide semiconductor device according to the first embodiment. The gas introduction amount of the gas containing Si and the gas containing C is preferably adjusted so that the ratio of the number of C atoms to the number of Si atoms (C / Si ratio) is 1.0. In addition, the gas introduction amount is preferably adjusted so that the ratio of the number of Cl atoms to the number of Si atoms in the gas containing Si (Cl / Si ratio) is, for example, 3.0.

Adjusting the introduction amount of each gas so as to satisfy the above C / Si ratio and Cl / Si ratio, and changing only the flow rate without changing the ratio of the introduction amount of the gas containing Si, the gas containing C and the gas containing Cl. By increasing the growth rate of the SiC epitaxial film 2 in proportion to the flow rate of the source gas. That is, the flow rate of the gas containing Si with respect to the flow rate of the H ₂ gas as the carrier gas by increasing only the flow rate without changing the ratio of the gas introduction amount of the gas containing Si, the gas containing C and the gas containing Cl. Ratio (Si / H ₂ ratio) is determined. Therefore, as shown in FIG. 2, the growth rate of the SiC epitaxial film 2 can be increased in proportion to the increase in the Si / H ₂ ratio.

FIG. 2 shows the relationship between the Si / H ₂ ratio and the growth rate in Example 1 manufactured under the following film forming conditions. In Example 1, monosilane (hereinafter referred to as SiH ₄ / H ₂ ) gas diluted with H ₂ and dimethylmethane (hereinafter referred to as C ₃ H ₈ / H ₂ ) gas diluted with H ₂ as source gases. Was used. HCl gas was used as the additive gas containing Cl. H ₂ gas was used as the carrier gas. Specifically, the film forming conditions of Example 1 are as follows.

The amount of gas introduced was adjusted so that the C / Si ratio was 1.0 and the Cl / Si ratio was 3.0. Then, H ₂ gas as a carrier gas is flowed at a flow rate of 20 L / min, the flow rate of SiH ₄ / H ₂ gas is 200 sccm, the flow rate of C ₃ H ₈ / H ₂ gas is 166 sccm, and the flow rate of HCl gas is 300 sccm. It was. Doping gas is not added. In Example 1, it was confirmed that a growth rate of about 102 μm / h was obtained.

In Example 1, the flow rate of the source gas when the growth rate of about 102 μm / h is obtained corresponds to the case where the Si / H ₂ ratio is 0.5. When the Si / H ₂ ratio is larger than 0.5, the inside of the reaction furnace is vigorously soiled and particles are likely to be generated in the SiC epitaxial film 2. For this reason, it is preferable to determine the flow rates of the gas containing Si, the gas containing C, and the gas containing Cl so that the Si / H ₂ ratio is 0.5 or less.

  Next, for Example 1, components of the SiC epitaxial film 2 were analyzed by glow discharge mass spectrometry. FIG. 3 is a table showing components of the epitaxial film grown by the method for manufacturing the silicon carbide semiconductor device according to the first example. As shown in FIG. 3, SiC epitaxial film 2 contains Si and C as main components in proportions of 60% and 40%, respectively. Further, in the SiC epitaxial film 2, S and Cl were detected as impurities in addition to Si and C as main components. In Example 1, the content of Cl remaining in the SiC epitaxial film 2 was 0.098 ppm. Therefore, it was confirmed that the content of Cl remaining in the SiC epitaxial film 2 is 0.1 ppm or less that does not cause the characteristic deterioration of the SiC epitaxial film 2.

  On the other hand, the content of S remaining in the SiC epitaxial film 2 was 0.036 ppm. As described above, when only the gas containing Cl is used as the additive gas, the SiC epitaxial film 2 can be grown at a growth rate of 100 μm / h or more as described above. Content will become larger than 0.02 ppm which is the upper limit which does not produce the characteristic deterioration of the SiC epitaxial film 2. FIG. Therefore, in order to reduce the S content in the SiC epitaxial film 2, it is preferable to use a gas further containing F as the additive gas.

In FIG. 3, the components other than Si, C, S, and Cl are below the measurement limit value of the GDMS device (in FIG. 3, <measurement limit value is indicated. The same applies to FIG. 4) and are not detected. Show. Moreover, since tantalum (Ta), niobium (Nb), and indium (In) may be mixed from inside the GDMS analyzer, accurate measurement values cannot be obtained. Moreover, since cesium (Cs) interferes with In and gold (Au) receives interference of a tantalum oxide cation (TaO ⁺ ), it cannot be measured accurately. For this reason, the numerical values of Ta, Nb, In, Cs, and Au are described as reference values, and description of quantitative values is omitted.

Next, in addition to the film formation conditions of Example 1, the growth rate of SiC epitaxial film 2 was measured when a gas containing F was used as the additive gas (hereinafter referred to as Example 2). Specifically, in Example 2, H ₂ gas is flowed at a flow rate of 20 L / min as a carrier, SiH ₄ / H ₂ gas or C ₃ H ₈ / H ₂ gas is used as a source gas, and HCl gas is used as an additive gas. And CF ₄ gas was used. More specifically, the film forming conditions of Example 2 are as follows.

The total amount of SiH ₄ / H ₂ gas, C ₃ H ₈ / H ₂ gas, and CF ₄ gas introduced was adjusted so that the C / Si ratio was 1.0. The total amount of SiH ₄ / H ₂ gas and HCl gas introduced was adjusted so that the Cl / Si ratio was 3.0. The flow rate of SiH ₄ / H ₂ gas was 200 sccm. The flow rate of C ₃ H ₈ / H ₂ gas was 159 sccm. The flow rate of HCl gas was 300 sccm. The flow rate of CF ₄ gas was 20 sccm. The Si / H ₂ ratio was set to 0.5. Doping gas is not added.

The ratio of the number of C atoms (C / H ₂ ratio), which is the sum of C atoms in CF ₄ gas and C atoms in C ₃ H ₈ gas, to the flow rate of H ₂ gas as the carrier gas is 0.5 It was. The ratio of the flow rate of CF ₄ gas to the flow rate of H ₂ gas as the carrier gas was set to 0.1. In Example 2, it was confirmed that a growth rate of about 98 μm / h was obtained. Thus, it is confirmed that the same growth rate as in Example 1 using only the gas containing Cl as the additive gas can be obtained in Example 2 using the gas containing Cl and the gas containing F as the additive gas. It was done.

Next, for Example 2, the components of the SiC epitaxial film 2 were analyzed by glow discharge mass spectrometry. FIG. 4 is a table showing components of the epitaxial film grown by the method for manufacturing the silicon carbide semiconductor device according to the second example. As shown in FIG. 4, the content of S remaining in the SiC epitaxial film 2 was 0.02 ppm or less, which is the measurement limit value of the GDMS apparatus, and was not detected. The reason is assumed that F in the CF ₄ gas reacts with S in the SiC epitaxial film 2 to become a gas such as SF ₆ and is discharged to the outside of the SiC epitaxial film 2.

The content of Cl remaining in the SiC epitaxial film 2 was 0.091 ppm. Therefore, also in Example 2, the content of Cl remaining in the SiC epitaxial film 2 is 0.1 ppm or less that does not cause deterioration of the characteristics of the SiC epitaxial film 2, and it is confirmed that it is substantially the same as in Example 1. It was. Therefore, by simultaneously adding HCl gas and CF ₄ gas to SiH ₄ gas and C ₃ H ₈ gas which are source gases, high-speed growth of the SiC epitaxial film 2 is realized, and S and Cl remaining in the SiC epitaxial film 2 are realized. It has been confirmed that impurities such as can be reduced.

(Embodiment 2)
The method for manufacturing the silicon carbide semiconductor device according to the second embodiment is different from the method for manufacturing the silicon carbide semiconductor device according to the first embodiment in that a gas containing Cl as an additive gas is used as a film formation condition for the SiC epitaxial film 2. The preferable range of the flow rate is set.

The growth rate of the SiC epitaxial film 2 was measured when the flow rate of the gas containing Cl was variously changed and the Cl / Si ratio was changed from 2.0 to 6.0 (hereinafter referred to as Example 3). FIG. 5 is a characteristic diagram showing the relationship between the amount of gas introduced and the growth rate of the epitaxial film in the method for manufacturing the silicon carbide semiconductor device according to the second embodiment. The film forming conditions of Example 3 are as follows. As source gas, SiH ₄ / H ₂ gas and C ₃ H ₈ / H ₂ gas were used as in Example 1. HCl gas was used as the additive gas. The flow rate of SiH ₄ / H ₂ gas was 150 sccm.

The flow rate of C ₃ H ₈ / H ₂ gas was set to 125 sccm. A plurality of examples 3 were manufactured by changing the flow rate of HCl gas from 150 sccm to 450 sccm. The Cl / Si ratio is 2.0 when the flow rate of HCl gas is 150 sccm, and the Cl / Si ratio is 6.0 when the flow rate of HCl gas is 450 sccm. Configurations other than the raw material gas flow rate, additive gas flow rate, and Cl / Si ratio in the method for manufacturing the silicon carbide semiconductor device according to the second embodiment are the same as those in the method for manufacturing the silicon carbide semiconductor device according to the first embodiment. .

  As shown in FIG. 5, the growth rate of the SiC epitaxial film 2 decreases when the Cl / Si ratio becomes 3.0 or more, and further rapidly decreases when the Cl / Si ratio becomes 5.0 or more. It was confirmed. Further, when the Cl / Si ratio is 2.0 or less, particles are generated in the SiC epitaxial film 2 and the contamination in the reaction furnace becomes more severe. The reason is that as the Cl / Si ratio is higher, the contamination in the reaction furnace due to the formation of the SiC epitaxial film 2 can be reduced. Therefore, in order to maintain the growth rate of SiC epitaxial film 2 and suppress the generation of particles in SiC epitaxial film 2, the Cl / Si ratio is preferably 2.0 or more and 5.0 or less.

  As described above, according to each embodiment, the introduction amount of the source gas contributing to the growth of the SiC epitaxial film can be increased by adding the gas containing Cl to the source gas. Thereby, compared with the manufacturing method of the conventional SiC semiconductor device which does not add the gas containing Cl, the growth rate of a SiC epitaxial film can be increased about 20 times.

  Further, according to each embodiment, by adding a gas containing Cl and a gas containing F to the raw material gas, Cl and F react with S, which is an impurity in the SiC epitaxial film, and the chloride system. And can be discharged out of the SiC epitaxial film as a fluoride-based gas. For this reason, it is possible to prevent impurities (S and Cl) remaining in the SiC epitaxial film and impurities contained in the 4H—SiC substrate from being taken into the SiC epitaxial film. Thereby, impurities remaining in the SiC epitaxial film can be reduced. Therefore, it is possible to grow a SiC epitaxial film with much less impurities than the conventional one.

  Further, according to each embodiment, by introducing a gas containing Si, a gas containing C, a gas containing Cl, and a gas containing F at an appropriate mixing ratio, Si, Impurities other than the n-type and p-type elements for doping the C and SiC epitaxial films can be made difficult to remain in the SiC epitaxial film. Therefore, it is possible to grow the SiC epitaxial film at a high speed and reduce impurities that cause the characteristics of the SiC epitaxial film remaining in the SiC epitaxial film to deteriorate.

  As described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present invention, the measurement limit value of the GDMS apparatus is described as an example. For example, the measurement limit value of secondary ion mass spectrometry (SIMS) or the like can be used to determine the amount of S in the SiC epitaxial film. You may set the upper limit of content.

  As described above, the method for manufacturing a silicon carbide semiconductor device according to the present invention is a case in which a transistor, a diode, or the like is manufactured using SiC as a semiconductor material, and a SiC single crystal film is formed on a SiC substrate. This is useful for a semiconductor device manufactured using a single crystal substrate.

1 4H-SiC substrate 2 SiC epitaxial film

Claims (6)

A silicon carbide semiconductor is formed on a silicon carbide semiconductor substrate by using a gas containing silicon and a gas containing carbon as a source gas, adding a gas containing chlorine and a gas containing fluorine to the source gas, and using a hydrogen gas as a carrier gas. Including the step of growing the film,
Adding the chlorine-containing gas within a range in which the ratio of the number of chlorine atoms to the number of silicon atoms in the gas containing silicon is 2.0 or more and 5.0 or less;
In the silicon carbide semiconductor device, the gas containing fluorine is added within a range in which the ratio of the number of fluorine atoms to the number of hydrogen atoms in the carrier gas is 0.1 or more and less than 0.2. Production method.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein a content of sulfur remaining in the silicon carbide semiconductor film is 0.02 ppm or less.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein a content of chlorine remaining in the silicon carbide semiconductor film is 0.1 ppm or less.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the gas containing chlorine is hydrogen chloride gas or chlorine gas.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the gas containing fluorine is a carbon tetrafluoride gas.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the silicon carbide semiconductor film made of a single crystal is grown by chemical vapor deposition.

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